Janus kinase inhibitors suppress cancer cachexia‐associated anorexia and adipose wasting in mice

Abstract

Background Cachexia, a syndrome of muscle atrophy, adipose loss, and anorexia, is associated with reduced survival in cancer patients. The colon adenocarcinoma C26c20 cell line secretes the cytokine leukaemia inhibitory factor (LIF), which induces cachexia. We characterized how LIF promotes cachexia-associated weight loss and anorexia in mice through Janus kinase (JAK)dependent changes in adipose and hypothalamic tissues. Methods Cachexia was induced in vivo with the heterotopic allotransplanted administration of C26c20 colon adenocarcinoma cells or the intraperitoneal administration of recombinant LIF in the absence or presence of JAK inhibitors. Blood, adipose, and hypothalamic tissues were collected and processed for cytokine/adipokine enzyme-linked immunosorbent assays, immunoblot analysis, and quantitative reverse transcription polymerase chain reaction (RT-PCR). Cachexia-associated lipolysis was induced in vitro by stimulating differentiated adipocytes with recombinant LIF or interleukin (IL)-6 in the absence or presence of lipase or JAK inhibitors. These adipocytes were processed for glycerol release into the media, immunoblot analysis, and RT-PCR. Results Tumour-secreted LIF induced changes in adipose tissue expression and serum levels of IL-6 and leptin in a JAK-dependent manner influencing cachexia-associated adipose wasting and anorexia. We identified two JAK inhibitors that block IL-6 family-mediated adipocyte lipolysis and IL-6 induction using an in vitro cachexia lipolysis assay. JAK inhibitors administered to the in vivo C26c20 cancer cachexia mouse models led to (i) a decrease in signal transducer and activator of transcription 3 phosphorylation in hypothalamic and adipose tissues, (ii) a reverse in the cachexia serum cytokine/adipokine signature, (iii) a delay in cancer cachexia-associated anorexia and adipose loss, and (iv) an improvement in overall survival. Conclusions JAK inhibitors suppress LIF-associated adipose loss and anorexia in both in vitro and in vivo models of cancer cachexia.

LIFR-α-dependent adipocyte signaling in obesity limits adipose expansion contributing to fatty liver disease

“…The adipocyte fractions were subjected to qRT-PCR, and Adipoq-Cre;LIFR fl/fl adipocytes demonstrated no detectable mRNA expression of LIFR , verifying disruption of the gene in adipocytes in the adipose tissue of the knockout animals ( Figure 1 C). Adipocytes from the LIFR knockout mice also had a significant decrease in IL6 expression compared with littermate controls, which is consistent with our previous findings that LIF increases IL6 expression in a JAK-dependent manner in differentiated adipocytes ( Arora et al., 2020 ). At the protein level, there was a significant reduction in LIFR-α in eWAT of knockout mice compared with controls, with equivalent hepatic levels of LIFR-α in knockout and littermate controls ( Figure 1 D).…”

“…We have now shown that LIF signals through its receptor LIFR-α to induce STAT3 activation and adipocyte lipolysis in adipose. We previously showed that LIF and other IL-6 family members increase the lipolysis potential of the adipocyte through a JAK-dependent mechanism ( Arora et al., 2020 ). Although we observed an association of STAT3 phosphorylation with LIF and IL-6-mediated lipolysis, there was no evidence that STAT3 was required for IL-6 family cytokine-mediated adipocyte lipolysis.…”

“…These cytokines are also associated with adipose inflammation in cachexia, a syndrome on the opposite end of the metabolic spectrum ( Arora et al., 2018 ; Auernhammer and Melmed, 2000 ; Seto et al., 2015 ). LIF signals through its canonical receptor LIFR-α ( LIFR gene) and co-receptor gp130 to activate the JAK/STAT inflammatory pathway ( Arora et al., 2018 , 2020 ; Song and Lim, 2006 ). LIF signaling in differentiated adipocytes leads to JAK-dependent STAT3 phosphorylation, which (1) increases basal level lipolysis to break down triacylglycerol (TAG) to glycerol and fatty acids and (2) increases expression of the gene encoding IL-6 ( IL6 ).…”

“…Although STAT3 phosphorylation is associated with IL-6 family-mediated lipolysis, its role in transmitting these cytokine signals in the adipocyte has not been established. Recombinant LIF (rLIF) administered to mice, including models of obesity, limits further adipose expansion leading to a decrease in adipose and body weight due to anorexia and adipocyte lipolysis signals that are in part due to JAK-dependent adipose inflammation ( Arora et al., 2018 , 2020 ). These wasting effects do not require IL-6 because rLIF treatment of global IL6 knockout mice yielded similar findings.…”

The Role of Tumor Microenvironment Cells in Colorectal Cancer (CRC) Cachexia

“…This, in turn, results in cachexia-associated adipose wasting as well as anorexia. The authors noted that the use of JAK inhibitors in both in vitro and in vivo models of CC inhibits this process [ 74 ].…”